Search for particle acceleration in two massive Wolf-Rayet stars using uGMRT observations

• Main Authors: Saha, Anindya, Tej, Anandmayee, del Palacio, Santiago, De Becker, Michaël, Benaglia, Paula, CH, Ishwara Chandra, Prajapati, Prachi
• Format: Journal Article
• Language: English
• Published: 09-09-2023
• Subjects: Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.2309.04736

Large wind kinetic power of Wolf-Rayet (WR) stars make them ideal targets in
low radio frequencies to search for non-thermal emission due to relativistic
particle acceleration. In this paper, we present observations of two WR stars,
WR 114 and WR 142, in Band 4 (550-950 MHz) and Band 5 (1050-1450 MHz) using the
upgraded Giant Meterwave Radio Telescope (uGMRT). Neither star is detected in
the observed frequency bands, nor extended emission associated with them. The
upper limit to the free-free radio emission from the stellar wind enables us to
constrain the mass-loss rate of WR 114 to $\lesssim \rm 10^{-5}\,M_{
\odot}\,yr^{-1}$; this is a factor three smaller than previously estimated
using spectroscopic modelling. If we further assume that the WR stars are
binaries, the non-detection of synchrotron emission from the putative wind
collision region implies that the stars are either in very wide binary systems
away from periastron, or that the stars are in close binary systems with an
orbital separation $<70$ AU for WR 114 and $<20$ AU for WR 142. The
non-detection of low-frequency radio emission from these two systems thus
provides evidence that narrows their nature, though it does not rule them out
as bonafide particle-accelerating colliding-wind binaries.